Is Voyager 1 in interstellar space now?

Yes. After a 47-year journey out of the Solar System, Voyager 1 has left the heliosphere - the region dominated by particles flowing out from the Sun in the solar wind.

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Scientists think it achieved this landmark around August 2012, when its detectors began to pick up increasing numbers of cosmic rays, which are high-speed particles from distant stars and galaxies. This indicates that it has crossed the heliopause - the boundary between the heliosphere and the interstellar medium – and is now drifting through a turbulent region just beyond the Sun's protective bubble.

WHEN IS A SPECIES CLASSED AS ENDANGERED?

The International Union for the Conservation of Nature (IUCN) maintains a 'Red List' of the world's endangered species. There are seven categories that range from Least Concern, through to Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and finally Extinct. Endangered species face a 'very high risk of extinction in the near future'. This takes into account the number of animals left, as well as their rate of decline and geographical distribution. Just under 170,000 of over 2 million known species are assessed each year. There are at least 38,500 species currently under threat, with over 16,300 considered endangered.

WHY DO MARTIAL ARTS HAVE BELT COLOURS?

Judo was the first martial art to award a 'black belt', introduced by its founder Kanō Jigorō. He was inspired by Japan's high-school swimming, where advanced students wore black ribbons. The other colours were introduced as a motivation tool by Mikinosuke Kawaishi, and this became so successful that other styles followed.

WHEN WERE CONTACT LENSES INVENTED?